Start using String type info:

src/type-info.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 23 matching lines @@
 
 
 TypeInfo TypeInfo::TypeFromValue(Handle<Object> value) {
   TypeInfo info;
   if (value->IsSmi()) {
     info = TypeInfo::Smi();
   } else if (value->IsHeapNumber()) {
     info = TypeInfo::IsInt32Double(HeapNumber::cast(*value)->value())
         ? TypeInfo::Integer32()
         : TypeInfo::Double();
+  } else if (value->IsString()) {
+    info = TypeInfo::String();
   } else {
     info = TypeInfo::Unknown();
   }
   return info;
 }
 
 
 } }  // namespace v8::internal